non kz rectifier question

Hi guys. Posting a question for a friend who owns a 1982 cb750s nighthawk. He had a rectifier burn out and bought a used one which also burned out. Then bought an after market rectifier. When bike is running , it draws 2 amps from battery without headlight on. With light on it draws 8 amps. Is this normal or is he in danger of burning out another rectifier ? any input would be appreciated .:sick:

I would expect that bike uses a solid-state, reg/rec combo unit. It uses an excited field alternator.

The regulator controls the current to the field coil to regulate the output from the alternator to the rectifier.

Where are you measuring the current?

The red wire is the output from the rectifier. On a Honda, the black wire is often 12 volts, while green is ground.

The white wire is the ground side of the field coil and is the wire controlled by the regulator. In other words, the regulator controls the ground connection of the field coil. The positive side is connected to 12 volts when the ignition switch is on.

measuring the current at the battery

those bikes are prone to electric problems but don't worry. they are repairable

have you checked the carbon brushes and slip rings on the rotor?

a short in the wiring to the stator, in the stator, and carbon brush holder may be the source of your problem.

also check insulation breakdown integrity of the stator winding before hooking up another genuine honda reg/rct

Sounds like the charging system is doing almost nothing. Does the battery voltage increase to about 14v when you rev it, with or without the headlight?

The most common problem I find on those Hondas is the field coil (rotor) goes bad. They usually fail in such a way that they test ok, but under load they fail from heat or vibration.

If the reg/recs are burning out, it can be that the rotor is shorted out or its wiring is shorted.